1. Field of the Invention
This invention relates to a method for the production of 3-cyano-3,5,5-trimethyl cyclohexanone. More particularly, it relates to a method for producing 3-cyano-3,5,5-trimethyl cyclohexanone in a stoichiometric yield by the reaction of isophorone with hydrogen cyanide under specific conditions in the presence of a quaternary ammonium salt or a quaternary phosphonium salt and a basic compound.
2. Description of the Prior Art
3-Cyano-3,5,5-trimethyl cyclohexanone is an industrially useful and important compound which, through hydrogenation and amination, produces 1-amino-3-aminomethyl-3,5,5-trimethyl cyclohexane to be used as a curing agent for epoxy resin and, further through isocyanation, produces 3-isocyanate methyl-3,5,5-trimethyl cyclohexyl-1-isocyanate to be used as a raw material for polyurethane coating material attracting attention especially for use in automobiles, powder coating material, quality elastomer, and leather surface treating agent.
It has been known to the art to produce 3-cyano-3,5,5-trimethyl cyclohexanone from isophorone and hydrogen cyanide or a cyanide as raw materials. By the method disclosed in J. Org. Chem., Vol. 13, pp. 31 to 37 (1948), for example, 3-cyano-3,5,5-trimethyl cyclohexanone is synthesized in a yield of 60% by one week reaction of isophorone with sodium cyanide at normal room temperature in a mixed solution of methanol, water, and acetic acid. It is self-evident, however, that this method is least feasible as a commercial process because it has low productivity and requires a time-consuming reaction. By the method disclosed in J. Am. Chem. Soc., Vol. 104, No. 23, pp. 6,449 and 6,450 (1982), 3-cyano-3,5,5-trimethyl cyclohexanone is synthesized in a yield of 63% by causing isophorone to react with t-butyl isocyanide in the presence of titanium tetrachloride of an amount substantially equimolar to the isophorone. This method has poor commercial feasibility because it suffers from poor productivity and necessitates use of expensive raw materials.
West German Patent No. 1,085,871 discloses a method for synthesizing 3-cyano-3,5,5-trimethyl cyclohexanone by causing isophorone to react with hydrogen cyanide in a polar solvent such as, for example, dimethyl acetamide in the presence of an alkali metal salt as a catalyst. British Patent No. 887,413 discloses a method for synthesizing 3-cyano-3,5,5-trimethyl cyclohexanone by causing isophorone to react with potassium cyanide in such a polar solvent as dimethyl acetamide. These methods are incapable of serving satisfactorily as commercial processes because they produce 3-cyano-3,5,5-trimethyl cyclohexanone only in a low yield of about 70% and call for an unduly large load in the recovery of a used solvent.
Further, Japanese Patent Publication SHO 40(1965)-7,486 discloses a method for continuously synthesizing 3-cyano-3,5,5-trimethyl cyclohexanone by supplying to an alkaline catalyst deposited on a solid carrier a gaseous isophorone-hydrogen cyanide mixture having a hydrogen cyanide content of not more than about 10% by weight based on isophorone. This method, however, is a problematic process from the commercial point of view because the catalyst is inevitably poisoned by the by-produced polymer of hydrogen cyanide and prevented from offering an appreciably long service life and the reaction entails recovery of a large amount of unaltered isophorone.
West German Patent No. 1,240,854 discloses a method for synthesizing 3-cyano-3,5,5-trimethyl cyclohexanone by causing isophorone to react with hydrogen cyanide in the presence of an alkali metal salt as a catalyst with methanol used as a dispersant for the catalyst. When this method was replicated, however, it was found that the reaction produced 3-cyano-3,5,5-trimethyl cyclohexane only in a low yield of about 70% and entailed by-production of a large amount of polymer of hydrogen cyanide. Thus, this method is problematic as a commercial process.
Japanese Patent Publication SHO 62(1987)-5,418 discloses a method for synthesizing 3-cyano-3,5,5-trimethyl cyclohexanone by causing hydrogen cyanide to react with a large excess of isophorone enough to preclude by-production of polymer of hydrogen cyanide in the presence of an inorganic basic catalyst and a glycol. When this method was replicated, however, it was found to be a commercially problematic process because it produced 3-cyano-3,5,5-trimethyl cyclohexanone only in a low yield of about 80% and necessitated recovery of a large amount of an unaltered isophorone.
Japanese Patent Publication HEI 1(1989)-47,459 discloses a method for synthesizing 3-cyano-3,5,5-trimethyl cyclohexanone by causing isophorone to react in a two-phase system with sodium cyanide or potassium cyanide dissolved as a cyanide in water in the presence of a phase transfer catalyst selected from among quaternary ammonium salts and quaternary phosphonium salts. This method, however, is not fully satisfactory because the conversion of isophorone is low in spite of the use of the cyanide in a large excess relative to isophorone, the amount of an unaltered isophorone to be recovered is consequently large, and the selectivity of the reaction for 3-cyano-3,5,5-trimethyl cyclohexanone is only about 90%. Since this method uses the solvent, it requires the solvent to be recovered from the reaction mixture. It further abhors use of hydrogen cyanide on account of the by-production of a polymer of hydrogen cyanide and the operational difficulty encountered in the use of this acid and resorts inevitably to use of sodium cyanide or potassium cyanide as a cyanide. In actuality, this cyanide is used in a very large excess falling in the range of from 1 to 10 mols per mol of isophorone. In this method, the cyanide remains in an unaltered form in a large amount after completion of the reaction and poses a difficult problem of handling. The patent publication has no clear mention about the solution of this problem. It may be added that when sodium cyanide or potassium cyanide dissolved in water is used as a cyanide as clearly mentioned in the patent publication, the alkalinity of the aqueous phase of the reaction system increases with the progress of the reaction. The reaction, therefore, entails a secondary operation of buffering the reaction system with an acid. In the light of these problems, this method does not deserve adoption as a commercial process.
Japanese Patent Laid-Open SHO 61(1986)-33,157 discloses a method for synthesizing 3-cyano-3,5,5-trimethyl cyclohexanone in a yield of about 95% by causing isophorone to react with hydrogen cyanide in the presence of a quaternary ammonium hydroxide or a quaternary phosphonium hydroxide. By this method, however, since the quaternary ammonium hydroxide or quaternary phosphonium hydroxide has strong basicity, such secondary reactions as the polymerization of hydrogen cyanide and such secondary reactions as the decomposition and polymerization of 3-cyano-3,5,5-trimethyl cyclohexanone formed during the course of the reaction are not easily repressed. The reaction, therefore, entails by-production of the polymer in a large amount and necessitates a difficult after-treatment. This method is also incapable of serving satisfactorily as a commercial process of the kind aimed at by the present inventors.
Japanese Patent Laid-Open SHO 61(1986)-33,158 discloses a method for synthesizing 3-cyano-3,5,5-trimethyl cyclohexanone by causing isophorone to react with hydrogen cyanide in the presence of a diazabicycloalkene as a catalyst. This method has the disadvantage that the catalyst to be used is expensive and the spent catalyst is not easily recovered for cyclic use and, because of the strong basicity of the catalyst, the reaction entails by-production of the polymer in a large amount. Thus, this method has much room for further improvement.
Inherently, hydrogen cyanide exhibits very low addition reactivity to the double bond of isophorone. Numerous measures, therefore, have been proposed as described above for the purpose of increasing the cyan ion concentration in the organic layer containing isophorone and consequently enhancing the reactivity of the reaction system. None of these methods, however, deserve to be called a fully satisfactory commercial process in terms of economy, productivity, operational efficiency, etc.
An object of this invention, therefore, is to provide a novel method for the production of 3-cyano-3,5,5-trimethyl cyclohexanone.
Another object of this invention is to provide a method for producing 3-cyano-3,5,5-trimethyl cyclohexanone in a stoichiometric yield while using hydrogen cyanide and yet precluding by-production of the polymer of hydrogen cyanide, obviating the necessity of using a solvent for solubilizing or dispersing a catalyst in isophorone, or requiring use of a large excess of either isophorone or a cyanide and consequently entailing recovery of a large amount of an unaltered raw material.